Assays of Homeopathic Preparations
AAHP calls attention to an article contending that, because homeopathic preparations are not governed by conventional dose-response relationships, assays and analytical markers often cannot be linked to the efficacy of the finished product.
These observations were presented by Dr. Michael Keusgen, Dean of the Department of Pharmacy and Professor of Pharmaceutical Chemistry at the Philipps-Universität Marburg in Germany, in “Quality Aspects of Homoeopathic Preparations,” published in the April 2013 edition of Pharmeuropa Online, a publication of the European Directorate for the Quality of Medicines & HealthCare (EDQM). (An account must be created to view the article through: http://pharmeuropa.edqm.eu/home/menupage/English/Reader’s%20Tribune/2013/RT2012_17en.pdf)
Professor Keusgen notes that chemically defined substances usually have a dose-response curve that defines efficacy, and thus assays are required for both quality and safety reasons. However, he goes on to state that homeopathic products are not subject to dose-response curves in which the concentration of the starting material is related to the efficacy of the product.* Therefore, physico-chemical assays are, by and large, not meaningful for these medicines.
An assay can be appropriate for some raw materials to establish identity and purity, such as chemicals and minerals. On the other hand, plant materials are a complex of many substances; consequently, an assay focused on just one component is not a relevant indicator of any quality aspects. In the same way, Professor Keusgen argues, analytical markers are also meaningless, as they, too, are not “related to the efficacy of the final homeopathic preparation.”
Regarding substances that are considered toxic (in pure form), Professor Keusgen states the concept of an “assay” is not “scientifically justified”; this is because an assay implies both an upper and a lower limit for acceptance. However, the homeopathic manufacturing method itself makes any lower limit acceptance criteria pointless. Therefore, for these substances, only an upper “limit test” is necessary for safety considerations.
*AAHP editorial staff update, June 2026: From a quality standpoint, specifications and testing against those specifications is fundamental to reproducibility and safety. While Dr. Keusgen was likely speaking of highly dilute homeopathic substances in his discussion of the dose response curve, not all homeopathic drug products are highly dilute. Dose response curve may apply therapeutically and from a safety standpoint.